Corrosion of fasteners in ACQ treated wood

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Corrosion of fasteners in ACQ treated wood

• Newsha Ashari and Sofya Soldkin
• Tree Island Industries Ltd.
• John N.R. Ruddick
• UBC

2

• Goals
• Compare the corrosion of fasteners in ACQ CCA
  treated wood.
• Identify the best nail coating suitable for ACQ
  treated wood.

3

• Materials
• Nails Selected for the Corrosion Test had been
  advertised by Suppliers to be suitable for ACQ
  application.
• ACQ CCA Wood samples were purchased from local
  Home Depot.

4
List of Nails Tested
5
List of Nails Tested
6
Corrosion Resistance Testing Protocol

• Testing for Mechanical Damage Prior to Exposure
  in Environmental Chamber.
• Exposure to the surface of treated wood.
  Duplicates the real life worst case scenario
  Corrosion under the head and between the two
  surfaces of the connected timber.

7
Corrosion Resistance Testing Protocol

• 4 Nails of each type driven into the wood
• Extracted by splitting the wood,
• Placed between the gaps of sandwiched ACQ CCA
  treated wood in a randomized positions.

8
Corrosion Resistance Testing Protocol

• Exposure to Continuous Water Fog (Moisture with
  no salt).
• Follow up investigation of the effect of Water
  Repellant on Corrosion of hot dipped galvanized
  nails in ACQ treated wood.

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Corrosion Resistance Testing Protocol

• Time Intervals in the Environmental Chamber
• 188, 380, 644, and 830 hours,
• Temp 49 C (120F)
• Continuous Water Fog.
• At each time interval, wood samples were removed,
  disassembled, and nails inspected visually

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Observations Results

• The testing was concluded after 830 hrs as
  perforation of coating the beginning of red
  rust was observed on HDG nails.
• Visual Inspection corrosion started earlier
  appeared more severe in ACQ compared to CCA
  treated Wood.

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Observations Results

• Methods Used to Evaluate Corrosion Level
• Visual Observation
• Diameter Loss (Steel Core Cross-Section
  Reduction)
• Weight Loss
• Bending Yield Strength Testing

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Observations Results

• HDG in ACQ Treated Wood (Visual Observation).

Corrosion test after 180 hrs.
Corrosion test after 644 hrs.
Corrosion test after 380 hrs.
Corrosion test after 830 hrs.
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Observations Results

• Coating 3 in ACQ Treated Wood (Visual
  Observation)

Corrosion test after 188 hrs.
Corrosion test after 644 hrs.
Corrosion test after 380 hrs.
Corrosion test after 830 hrs.
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Observations Results

• Coating 4 in ACQ Treated Wood (Visual
  Observation).

Corrosion test after 188 hrs.
Corrosion test after 644 hrs.
Corrosion test after 380 hrs.
Corrosion test after 830 hrs.
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Observations Results

• Coating 5 in ACQ Treated Wood (Visual
  Observation)

Corrosion test after 644 hrs.
Corrosion test after 188 hours.
Corrosion test after 830 hrs.
Corrosion test after 380 hrs.
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Observations Results

• Stainless Steel in ACQ (Visual Observation)

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Observations Results

• Bright Nail in ACQ Treated Wood (Visual
  Observation).

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Observations Results

• Coating 8 in ACQ Treated Wood (Visual
  Observation).

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Observation Results

• Diameter loss (Steel Core Cross-Section
  Reduction)
• Measured with Caliper to the accuracy of 0.0001
  inch

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Observations ResultsCross-Section after
Corrosion imposed on the original.

• Coating 3 Coating 4
  Coating 5 Hot Dip Galv.

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Observations Results

• Weight Loss.
• Ultrasonic Bath used to clean the corrosion
  Products.
• Less Accurate than Diameter Measurement Due to
  Difficulty of Removing Corrosion Products.

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Observations Results (Cont.)
23
Observations ResultsBending Yield Strength
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Summary

• The Reason for Higher Fasteners Corrosion Rate in
  ACQ compared to CCA is due to the
• Larger amount of copper in ACQ. Copper is
  Noble metal and causes electrochemical reaction
  with less Noble metals
• Active ingredients in ACQ not corrosion
  inhibitors chrome arsenic in CCA serve as
  inhibitors
• Quat in ACQ is surfactant - absorbs water.
  Chromate in CCA is water repellant, lowers
  moisture content.

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Summary

• Best Nail Coating Suitable for Use with ACQ
  Treated Wood.
• Stainless steel has an outstanding performance
  compared to any nail coating. It has the similar
  electrochemical potential as copper, hence no
  copper induced corrosion.
• TII Hot Dip Galvanized after forming to ASTM
  A153 Class D demonstrate good performance in the
  ACQ treated wood.
• All other coatings show higher corrosion rate
  compared to HDG nails.